1. Field
Disclosed embodiments are generally related to fuel injectors for a gas turbine, and, more particularly, to fuel injectors including tandem vanes for injecting alternate fuels, such as may comprise fuels having a different energy density.
2. Description of the Related Art
Economic considerations have pushed the development of gas turbines capable of using alternate fuels, such as may involve synthetic gases (e.g., syngas) in addition to using fuels, such as natural gas and liquid fuels, e.g., oil. These synthetic gases typically result from gasification processes of solid feedstock such as coal, pet coke or biomass. These processes may result in fuels having substantially different fuel properties, such as composition, heating value and density, including relatively high hydrogen content and gas streams with a significant variation in Wobbe index (WI). The Wobbe index is generally used to compare the combustion energy output of fuels comprising different compositions. For example, if two fuels have identical Wobbe indices, under approximately identical operational conditions, such as pressure and valve settings, the energy output will be practically identical.
Use of fuels having different fuel properties can pose various challenges. For example, as the heating value of the fuel drops, a larger flow area would be required to deliver and inject the fuel into the turbine and provide the same heating value. Thus, it is known to construct different passages for the injector flow to accommodate the Wobbe index variation in the fuels. Another challenge is that fuels having a high hydrogen content can result in a relatively high flame speed compared to natural gas, and the resulting high flame speed can lead to flashback in the combustor of the turbine engine. See U.S. Pat. Nos. 8,661,779 and 8,511,087 as examples of prior art fuel injectors involving vanes using a traditional jet in cross-flow for injection of alternate fuels in a gas turbine.